The present disclosure relates to an illuminating device illuminating, for example, a transmissive liquid crystal panel from behind and a display unit including the same.
In the past, as a display unit of a word processor, a laptop personal computer or the like, a liquid crystal display unit in which a backlight (illuminating device) is arranged behind a liquid crystal panel has been used. As the illuminating device for the liquid crystal display unit, for the purpose of realizing a light-weight and thin body, an edge light type illuminating device in which a linear light source such as a fluorescent lamp is arranged on the side edge section of a light guide plate and a liquid crystal panel is arranged over the light guide plate has been mainstream. However, as the display unit has grown in size for the use of a television or the like in recent years, it is often the case that the luminance is not sufficient in the foregoing edge light type illuminating device. Thus, in recent years, a direct type illuminating device in which a linear light source is arranged directly beneath the liquid crystal panel has been used. (Patent Document 1)
[Prior Art Document]    Patent document    Patent Document 1 WO2006/071616
As display units have grown in size and have been thinned, illuminating devices have grown in size and have been thinned, as well. In result, there is a tendency that the number of linear light sources used for the illuminating device is increased, and a clearance between a tabular optical device arranged directly above the linear light sources and the linear light sources becomes narrow. If the number of linear light sources is increased, electric power consumption of the illuminating device is increased and electric power consumption of the television is also increased. Thus, it is conceivable that the number of linear light sources is not increased as much as possible, that is, a clearance between adjacent linear light sources is increased and thereby the increase amount of electric power consumption is inhibited. However, in this case, there are issues that in-plane luminance of illuminating light beam of the illuminating device becomes high in the position directly above the linear light sources, becomes low in the position directly above the central section between the linear light sources, and luminance unevenness is generated in a plane. Further, in the case where the clearance between the tabular optical device arranged directly above the linear light sources and the linear light sources is narrowed, again, there is a problem that luminance unevenness is generated in a plane.
Thus, a measure that a plurality of nonspherical convex sections in the same shape are provided in a plane on the light emission side of a diffusion plate formed by dispersing a diffusion material (filler) therein has been proposed. Thereby, not only the diffusion effect by the filler, but also diffusion effect of light directly above the linear light sources by the nonspherical shape is obtained, and accordingly the luminance unevenness is able to be resolved. However, such effect is limited, and widening the clearance between adjacent linear light sources or narrowing the clearance between the linear light sources and the optical device is not able to be realized much. Thus, it is further conceivable that a convex section is in the shape of a prism in the position directly above the central section between linear light sources, and thereby the front luminance in the position directly above the central section between the linear light sources is increased. However, in this case, there is a problem that though in-plane luminance unevenness when viewed from the front face is able to be resolved, in-plane luminance unevenness when viewed from a diagonal direction is deteriorated.
It is therefore desirable to provide an illuminating device with which not only in-plane luminance unevenness when viewed from the front face direction, but also in-plane luminance unevenness when viewed from a diagonal direction is able to be decreased and a display unit.